1. Field of the Invention
The present invention relates to shift control methods/systems for at least partially automated vehicular mechanical transmission systems including control techniques wherein the engine gross output torque required to cause zero drive line torque (i.e., zero flywheel torque) under current vehicle operating conditions is determined and, under various predetermined conditions, the engine is caused to generate such gross output torque. The shift control of the present invention uses torque information from the engine (preferably an electronic engine communicating over an electronic data link), along with vehicle and/or engine acceleration information, to determine various control parameters.
2. Description of the Prior Art
Fully automatic and semi-automatic vehicular mechanical transmission systems and fully or partially automated shift implementation systems utilizing electronic control units, usually microprocessor-based controllers, are known in the prior art. Examples of such automated mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,361,060; 4,425,620; 4,595,986; 4,631,679; 4,648,290; 4,722,248; 5,038,627; 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; 5,089,965; 5,133,229; 5,172,609; 5,231,582; 5,272,939; 5,335,566; 5,435,212; 5,508,916 and 5,509,867, the disclosures of which are incorporated herein by reference.
In accordance with an improved vehicular transmission control, an at least partially automated vehicular mechanical transmission system which accurately determined a value indicative of engine flywheel torque under current vehicle operating conditions was provided. That control is particularly useful for vehicular automated mechanical transmission systems communicating with an electronically controlled internal combustion engine by means of a data link of the type conforming to an industry-established protocol similar to SAE J 1922, SAE J 1939 or ISO 11898.
In a preferred embodiment of the improved control, the foregoing was accomplished in a vehicular automated mechanical transmission system control by utilizing the relationship that:
TEG=TFW+TBEF+TACCES+TACCEL 
where:
TEG=gross engine torque;
TFW=engine flywheel torque;
TBEF=base engine friction torque (includes the torque to overcome engine internal friction and the torque to rotate the engine manufacturer-installed accessories (i.e., water pump, oil pump, etc.));
TACCES=accessory torque (torque to operate vehicle accessories, such as air-conditioning, fans, lights, etc.); and
TACCEL=torque to accelerate engine, calculated from engine acceleration or deceleration and moment of inertia (I) of engine.
Instantaneous values representative of gross engine torque (TEG) and base engine friction torque (TBEF) are available on the data link. TACCEL is determined from sensed engine acceleration (which may be negative) and a calibrated moment of inertia (I) of the engine. Accessory torque (TACCES) is a constantly determined value which, Applicant has determined, may be taken as net engine torque (i.e., TEGxe2x88x92TBEF) if the vehicle is idling with the transmission in neutral and is related to engine deceleration rate in a known, substantially linear manner when the vehicle is in motion.
An adaptive control system/method for an at least partially automated vehicular mechanical transmission system which continuously updates the value of a control parameter (TFW) indicative of flywheel torque may be seen by reference to aforementioned U.S. Pat. No. 5,509,867.
In accordance with the present invention, Applicant has determined that under certain predetermined vehicle operating conditions, transmission performance may be improved by causing flywheel torque (which is generally equal to drive line torque with the master clutch engaged) to equal zero or substantially zero, that the gross engine output torque TEG required to cause a zero flywheel torque condition under the current vehicle operating conditions may be determined, and that the engine may be controlled to generate such a gross engine output torque.
Accordingly, it is an object of the present invention to provide a control for at least partially automated transmission systems wherein, under predetermined operating conditions, gross engine output torque is caused to equal a value which, under sensed vehicle operating conditions, will result in a zero engine flywheel/drive line torque.
This and other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment taken in connection with the attached drawings.